Telephone system



July 11, 1933.

W. SAVILLE TELEPHONE SYSTEM Filed Feb. 28, 1931 F5 i s I has [mask Im.refi ar- Millie Saprilla Patented July 11, 1933 i UNITED STATES PATENT OFFICE,

I WILLIE SAVILLE, OF LIVERPOOL, ENGLAND, ASSIGNOR' TO ASSOCIATED TELEPHONE AND TELEGRAPH COMPANY, OF CHICAGO, ILLINOIS, A CORPORATION OF DELAWARE TELEPHONE SYSTEM Application filed February 28,

The present invention relates to telephone systems and is particularly concerned'with metering on the so-called booster principle according to which the operation of a meter is effected by modifyingthe current flow over a conductor used for other purposes. The arrangement usually employed in known systems is that the mete is connected to the holding conductor and is operated by in- .creased current thereover due to the connecting up of a separate booster battery which serves to augment the normal exchange battery voltage. The arrangement in its simplest form however is not quite satisfactory where it is required to operate the meter-more than once during any one connection as for instance in a zone metering system. In

this case when the potential on the holding conductor is restored to normal the meter is likely to remain operated unless it has been very carefully and accurately adjusted. The object of the present invention is to provide a metering arrangement which while as simple and reliable as the known arrangement for single metering possesses operating margins sufi'iciently wide to permit multiple metering to be readily carried out,

According to the invention the operation of the meter is effected by the application of alternating current to the holding conductor to produce a reversal of current flow .in the meter circuit and when the current flow is restored to normal there is no doubt that the meter will release.

The invention will be better understood from the following description of one methml of carrying it into effect reference being had to the annexed drawing which shows diagrammatically the essential elements of a wellknown boost-er metering circuit to which the invention has been applied. The connections shown extend I through the calling partys line switch LS, the first group selector 1G8, the second group selector QGS and the final selector FS. It will be seen that little change has been made in the known circuits the diilerences being that the meter is connected to the holding conductor through a non-inductive resistance NI and is shunted by a rectifier couple RC preferably of the copper til the called party 1931, Serial No. 5i8,942,- and in. Great Britain May 6, 1930.

oxide type and that when metering is to take place the secondary winding of the ringing transformer RTis connected up in place of the'usual booster battery.

lVhen the connection has been set up and the wanted party is being rung, relays B and J are operated and the former extends earth from the resting contacts of the back bridge relay Dto hold, operated the switching relay H1 and H251 the group selectors,uand-the bridge-cutofi' relay BOO in the calling partys lineswitch. The meterM is also connected to the holding conductor but is erative at this time, since the rectifier RC is connected across its winding' in such direction as to provide a short-circuiting path under these conditions that the non-inductive resistance NI which is conveniently wound on the meter coil is intro duced into the circuit to prevent the current flowing throughtherectifier causing execs sive'heating and also to prevent therectii'ier shunting too much current fromthe holding relays.

No further circuit changes take place unanswers whereupon re lay D operates to-op'en the circuit of relay J and, during the slow release period of this latter relay ringing current by way of the ringing transformer ET is connected to the holding conductor in place of the-normal earth connection. Since the ringing potential isgreater than the battery potential and is of an alternating nature the meter will continue to be short-circuited by way of the rectifier RC during one half of the cycle while the other half will be effective to bring about its operation. Although in these circumstances the meter coil is only intermittently energized, the short-circui ti ng ell ect of the rectifier RC during the non-energized periods is sufiicient to maintain a holding flux in the coil so that the armature is held continuously and only one meter operation takes place for each application of ringingcurrent. Similarly the shunting effect of the rectifier prevents the. release of the holding "relays whentheir' normal energizing current is reversed.

hen relay 'J falls away, earth, over its inop- It should be mentioned resting contact-s will be re-applied to the holding conductor to maintain the relay BCO, H1 and H2, and the meter M will then restore owing to the prolonged shunting ef- 5 feet of the rectifier RC. Clearly therefore constantly maintained to prevent release of an established connection means for introducinga source ofalternating current, in:tho holding circuit, to operate the meter; and means for preventing its being repeatedly c operated during the time the alternating current remains i in the holding circuit.

2. In atelephoneisystem wherein acalling subscribens meteris operatedover a holding conductor overwhich. a current flow must be 1 constantly maintained to prevent release of an established connection means for-introducing asource of alternatmg current, 1n. the

holding circuit, to operate the meter; and

means connected in-the holding circuit, in

ammultiple with the meter, for preventing its being repeatedly operated duringthe time the alternating cur-rent 1 remains inthe holding circuit.

3; In a telephone system-whereina calling at subscribe1"s-1neteris operated over a holdingconductor by application of, an auxiliary potential thereto; the provision of me'ans enabling the employment of alternating current as the auxiliary potential for operating 40 the meter; said means beinget'f'ect-ive,-after the first. operation of themeter, to 'prevent subsequent operations thereofresulting from thealtern ations of the-alternating-current;

conductor by application of an auxiliary potentialthereto; the provision'of-a rectifier unit connected in multiple with the meter, to shunt current from it, and thus *PIBVBIIFItS' 5Q operation by current normally flowing-over the holdingcircuit; and means for-connecting nieteroperating current to the holdingconductor in the reverse direction to that normally employed, said'rectifier unit func tioninginthe-latter instance as a highresistance to enable suflicient current to flow through the meter tooperate it.

In a telephone system including arrangements for metering by modifyingthe current flow overva holding and guarding conductor,

in which the mcter is connected-t0 the holdingconductor andwto a pole'ofpotential opposite to thatrepresented by holding potential; a rectifier unit connected in parallel with .the 'meter insuch a directiomas to shunt it would now be possible to operateit' again it when normal holding potential is applied to the conductor, and as to offer a high resistance to the current flow over the conductor when modified to operate the meter.

6. In a telephone system wherein a calling' subscribers. meter isoperated over a'holding-conductori over which a current fiow'must be constantly maintained to prevent release of anestablishedconnection; arectifier unit connected in multiple with tlieineter is to shunt it andthus prevent it from being operated. bythe normal holding current, and a resistance included in the circuit to limit the shunting eftectofthe rectifier, on the equipment being held by the holding conductor.

7. Ina.telephonesystem, aswitch train employediin: extending a connection between a calling and'a called'line, respectively a holding circuitfortheswitches of said train including ameter for registering charges to be made for calls extended over-the calling-line: means insaid circuit for preventing holding current, normally supplied over sai'd circuit. from operating said meter, and means for substituting for the normallysupplied 1 holding current an alternating current of h igher potential thanthatof the holding cur-rentto operatesaidmeter, said means invsaid cir cuit also-serving to assist said alternating current to-maintainthe meter operated for the entire period during which the alte rn a ting currentremains connected in thecircuit.

8. Ina telephonesystem, aholding circuit, formaintaining-previously operated switches: employed inestablishing a telephoneconn ction, betweentwo subscribers stationsv imthe periodiof the-connection, a meterin said circuitforregistering charges to be made to: such-connection; a device connected in said circuitin multiplewith said meter normally preventingits-operation,but of assistance in maintaining saidineter in its operated posi- V tion afteroperation thereof: a source of a 4. In atelephone systemwherema-callmg e5--subscribe1-s meter is operated-over a-hold ng ternatingcurrent, andmeans for connecting said source to said' holding circuit to operate said meter.

9. Ina telephone system wherein a sci" of switches are employedto set up aconnrwtion between two subscribers stations and wherein-the switches are held in their operated-positionfor the duration of the connection over a holding circuit, the combination with saidholding circuit of a meter and meter controlling device traversed'by current flowing in said-holding circuit, and means for applyingasource of. alternating current of higherpotentialthan.the holding current to the-holdingcircuit-to operate said'meter, said meter-con trolling device preventing the meter from subsequent operation s otherwi se resu l ting-fronralternations inthe alternating current source.-

In testimony whereof-I aflix my signature.

WILLIE SAVIIJLE; 

